This invention is in the field of the cutting and non-cutting forming of metals. It relates to a novel process for using the required cooling lubricants.
Examples of the cutting machining (=forming) of metals are cutting, drilling, turning or mining, and examples of non-cutting forming are deep-drawing and massive forming. Liquid auxiliaries, so-called cooling lubricants, are required for those processes. The function of those auxiliaries is essentially to reduce friction between tool and workpiece, to dissipate the heat that is formed and to remove abraded metal (fine abraded material, dusts) or chips. They must also prevent discoloration and/or corrosion of the machined workpieces.
An overview of the shaping metal-working processes and the auxiliaries customarily used therefor will be found, for example, in Ulimann""s Encyclopedia of Industrial Chemistry, 5th Ed., Vol. A15, 479-486. The auxiliaries that come into consideration are in forms ranging from oils to oil-in-water emulsions to aqueous solutions. Usually there are added to the base liquids, oil or water, further components, such as viscosity regulators, antifoamers or corrosion inhibitors. Especially in the case of oil-based systems, lubricating additives, for example so-called xe2x80x9cEP additivesxe2x80x9d, are also customary. For the formation of emulsions, the use of emulsifiers is generally required; in many cases, the agents are also stabilised with biocides.
The oily components used nowadays are preferably paraffin oils or mineral oils. In addition, so-called synthetic lubricants (xe2x80x9csynthetic oilsxe2x80x9d), such as polyolefins, also come into consideration. Other examples of oily components are ester oils, which may be based on vegetable or animal oils, acetals or dialkyl ethers. By selecting the oils and mixtures thereof according to properties, such as polarity or viscosity, it is possible to formulate metal-working agents that meet the technical requirements of a very wide variety of fields.
In order to display an adequate lubricating action, the cooling lubricants must contain components having a lubricating action. In the case of water-soluble cooling lubricants that do not contain an oily phase, polyglycols are frequently used as the lubricating component. Although such aqueous cooling lubricants effect good heat dissipation, the lubricating action thereof is limited. On the other hand, substantially anhydrous oils may be used as cooling lubricants. They exhibit a very good lubricating action and, owing to the hydrophobic nature thereof, also a very good anti-corrosion action, but the rinsing and cooling action thereof is limited because of the viscosity and the low heat capacity of the oils. The use of oils as cooling lubricants has various disadvantages: The high price of the oils and the expenditure on maintenance required, for example, because the resulting chips and swarf are difficult to filter off, lead to high costs. Disposal of the resulting oil-impregnated chips and swarf poses problems, since they may lead to deflagrations or explosions, for example on attempted metallurgical reprocessing. The oil/air mixture that forms at the processing machine may also lead to explosions or deflagrations. For that reason the machines are encased, at great expense, in order to prevent the uncontrolled admission of air. Before the machine is opened, for example in order to change the workpiece, the oil-containing air must first be removed by suction through filters, which slows down the production cycles.
Cooling lubricants in the form of oil-in-water emulsions represent a widely used compromise as regards costs and expenditure, heat dissipation, lubricating action and corrosion protection. Those emulsions generally contain from about 0.05 to about 5 wt. % of an oily phase, which is dispersed in the aqueous phase with the aid of emulsifiers in the form of droplets in the submicrometer and micrometer range. A further important constituent of such cooling lubricant emulsions are corrosion inhibitors.
In order to improve the lubricating action of purely oily cooling lubricants (which are also known as cutting oils or forming oils) or of oil-containing cooling lubricant emulsions, so-called EP additives are frequently added. Those additives may be selected from organic compounds containing phosphorus, sulfur or, where demands as regards environmental protection are not as great, chlorine. Organosulfur compounds in particular are frequently used as EP additives.
An object of the present invention is to provide a process for the cutting or non-cutting forming of metals that is optimised both as regards lubrication and as regards cooling and the removal of chips.